1. Field of the Invention
The present invention relates to an organic electroluminescent device and a method of manufacturing the organic electroluminescent device, and more particularly to a technology for solving a problem of a defect of luminescence in an organic electroluminescent device.
2. Description of the Related Art
Organic electroluminescent displays (hereinafter, also referred to as “organic EL displays” or “organic EL panels”) are attracting attention as new flat-type displays. In particular, active matrix type organic EL displays having thin film transistors (hereinafter, also referred to as “TFTs”) as switching elements are regarded as sweeping out the currently prevailing liquid crystal displays in the near future, and are in a fierce development race for practical application.
FIG. 1 schematically shows the sectional structure of a typical organic electroluminescent device (hereinafter, also referred to as “organic EL device”). The organic EL device 100 has the structure in which an anode layer 20, an organic luminescent element layer 80, and a cathode layer 60 are laminated on a substrate 10 in order. The organic luminescent element layer 80 includes organic layers which function as a luminescent element such as a hole transporting layer 30, a luminescent layer 40, and an electron transporting layer 50, which are laminated on the anode layer 20 in this order. When a voltage is applied across the anode layer 20 and the cathode layer 60, holes injected from the anode layer 20 are transported to the luminescent layer 40 by the hole transporting layer 30. Electrons injected from the cathode layer 60 are transported to the luminescent layer 40 by the electron transporting layer 50. The electrons and the holes are recombined with each other at the interface or inside of the luminescent layer 40. The resulting energy excites electrons in the organic molecules of the luminescent layer 40. Then, the excited electrons relax with fluorescence emission. At least either one of the anode layer 20 and the cathode layer 60 is made of a transparent or semi-transparent material that transmits light of visible light range. The light emitted from the luminescent layer 40 is taken out through the electrode layer.
As above, unlike liquid crystal displays, organic EL displays have self-emission devices. This eliminates the need for a backlight which is indispensable to liquid crystal displays, promising apparatuses of yet lower profile and lighter weight. When poor luminescence occurs for any reason, however, dead pixels appear on-screen with deterioration in screen visibility, sometimes presenting an obstacle to the display function. It has therefore been a significant challenge to ascertain the cause of the poor luminescence and prevent it effectively so that organic EL displays having fewer dead pixels or no dead pixel can be fabricated with high yield.